Twisted splitter for fluid stream



United States Patent l 13,538,982

[72] Inventor Bruno M. Flori I 56] References Cited Farmington, Connecticut [2|] AWL 313,782 UNITED STATES PATENTS V .21, 1969 u 523 lo 1970 1,951,812 3/1934 Smlth 48/180(MU)X [73] Assignee United Aircraft Corporation l 9/1934 Hlgley 138/39 East Hartford, connectkut 3,266,524 8/1966 Goettl 138/37 acurpomuon Delaware 3,273,598 9/1966 Goettl 138/37 Continuation-impart of Ser. No. 588,051, Oct. 20, 1966, abandoned TWISTED SPLITTER FOR FLUID STREAM Claims, 5 Drawing Figs.

[1.8. CI. 165/7, 1 165/109,138/37,48/180 Int. Cl. F23] /02, F29f 13/12,F15d 1/02 Field ofSearch 138/37, 38,

39, 40, 42, 41,43 46; 109T, 7; 137/(Inquil'ed) 1 10/(Considered); l8l/(C0nsidered):

25 l/(Considered): 302/(Considered); 48 180, M,

Primary Examiner-H. Hampton Hunter Attorney- Fishman and Van Kirk varying cross-sectional entrance area. The divider forms two sections of reversing variable cross section along the length of the duct.

COMPRESSOR DISC J ARG E AIR FROM REGENERATOR, 2O

DIRECTION OF ROTOR AND MATRIX 34 PACKAGE, 3s

Sheet INVENTOR.

BRUNO M. FIORI ATTORNEYS! memed Nov. 10, 1970 3,538,982

Sheet 2 of 2 DIRECTION OF ROTOR, 34 AND MATRIX PACKAGE, 38

54 COMPRESSOR DISCHARGE AIR FRO M REGENERATOR,

INVENTOR BRUNO M. FIORI 1 TWISTED SPLITTER FOR FLUID STREAM CROSS-REFERENCE TO RELATED APPLICATION BACKGROUND OF THE INVENTION This invention relates to a mixer for mixing a fluid to reduce or eliminate temperature differentials in the fluid. More particularly, this invention relates to' a twisted splitter for dividing and mixing a fluid stream to reduce or eliminate temperature differentials in a fluid stream.

In many systems, it is desired to employ a heated fluid stream for a particularpurpose, and it is also desired that the fluid berelatively free of temperature gradients which might interfere with effective use of the fluid. However, temperature differentials may be created in the fluid in the'process of adding the desired heat to the fluid, and then the problem of eliminating or reducing temperature differentials must be solved.

By way of specific example, in a regenerative gas turbine enpressor to preheatthe air prior to delivery of the air to theburner section. One method of accomplishing this transfer of heat from the turbine exhaust stream to the compressor discharge air is to pass a heat exchanger matrix through the turbine exhaust stream to absorb heat from the turbine exhaust stream and then pass the heated matrix through the compressor discharge air streamto thus heat the compressor discharge exhaust stream. An example of such a system may be seen in the US. Pat. No. 3,l77,928 assigned to the assignee of the present applicationand to which reference is hereby made for incorporation herein. However, as can be seen in the referenced patent, when heatisto be added to a stream by placing the stream into an essentially crosscurrent heat exchange relationship 'withaheat source, a temperaturedifferential occurs in the heated stream due merely to the fact that the heat source, of necessity, decreases in temperature as it passes through the stream to be heated and thus has less heat available as it passes across the stream.

This temperature differential can reduce the effectiveness of the heated stream in many applications, and it thus becomes desirable to eliminate the temperature differential. For example, in.a regenerative gas turbine engine such a tem peraturedifferential in the air stream being delivered to the combustion section can result in unevenburning in the combustion section, and thus have deleterious effects which are reflected throughout the entire performance of the engine.

SUMMARY OF THE INVENTION In the present invention, the temperature differential in a fluid stream is eliminated or substantially redueedby passing the fluid stream through atwisted splitter device which mixes the fluid streamprior to its beingdelivered for its desired use. The twisted splitter of the present invention divides the fluid stream having the temperature differential into two or more parts and then causes an intermixing of parts at different temperature levels so that the fluid stream exiting from the device is a relativelywell mixed and relatively even temperatured fluid stream. The splitter of the presentinvention employs a sheet metal element which is twisted along the direction of fluid flow in a duct and which is arranged to gather different amounts of fluid at different temperatures and mix the different amounts of fluids at different temperatures as the fluid stream passes along the duct to provide a fluid stream of rela- Itively uniform temperature.

While the. present invention will be described in the environment of a regenerative gas turbine engine, it will be un derstood that the invention is not limited to such an environment. Rather, the invention may find general utility in the reduction or elimination of temperature differentials from a fluid stream, particularly in systems where it is desirable to eliminate a temperature differential resulting from a crosscurrent type of heat exchange.

Accordingly, one object of the present invention is to provide a novel mixing device for eliminating or reducing a temperature gradient in a fluid stream.

Another object of the present invention is to provide a novel flow splitter for mixing a fluid stream to eliminate or reduce a temperature gradient in the stream.

Still another object of the present invention is to provide a novel twisted flow splitter for mixing a fluid stream to eliminate or reduce a temperature differential in the stream.

Still another object of the present invention is to provide a novel mixing device for eliminating or reducing a temperature differential in a crosscurrent heat exchange system.

Still another object of the present invention is to provide a novel mixing device for use in a regenerative gas turbine engine to eliminate or reduce a temperature gradient in the air stream delivered to the combustion chamber.

'Other objects and advantages will be apparent from the following detailed descriptions and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, wherein like elements are numbered alike in the several figures;

FIG. I is a view, partly in section, of a regenerative gas turbine engine.

FIG. 2a is a view along lie line 2a-2a of FIG. I showing the twisted splitter of the present invention.

FIG. 2b is a view along line 2b-2b of FIG. I showing the entrance from the turbine section of the regenerator.

FIG. 3 is a perspective view showing the twisted splitter of the present invention.

FIG. 4 is a drawing of a modification of the twisted splitter of the present invention incorporating a multiple or cascaded splitter.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, a regenerative gas turbine engine 7 pressed for further use in the engine. The compressed air from the compressor section 14 is then delivered through a diffuser section 16 and a duct 18 to aregenerator inlet 19 and thence to a regenerator heat exchanger 20. The compressed air is heated as it flows through regenerator heat exchanger 20 in the direction of the arrow. This heated air then passes through regenerator outlet passage 21 to twisted splitter 22 constituting the present invention where it is mixed to eliminate or reduce temperature gradients, outlet 21 having the same cross-sectional shape as shown for splitter 22 in FIG. 2a. The mixed and substantially uniform temperature air is then delivered to combustion chamber and turbine section 24 for fashion. The hot turbine exhaust gases are then passed via turbine exhaust duct 26 to regenerator air inlet passage 28, and thence through regenerator 20 in a direction indicated by the arrows to transfer heat to the regenerator. After passing through the regenerator, the turbine discharge air is then discharged through outlet 30 to the atmosphere or other point of discharge. For a more detailed description of a regenerative gas turbine engine, reference is again made to US. Pat. No. 3,177,928.

As is more fully described in U.S. Pat. No. 3,177,928, regenerator 20 includes an annular housing 32 in which an annular rotor 34 is mounted for rotation. Rotor 34 is of generally circular cross section and rotates about a point on axis line 36. Rotor 34 is generally hollow and is constructed of a skeleton framework to allow the passage of air and gases through the regenerator. Heat absorbent matrix packages 38are mounted within rotor 34, and the rotation of rotor 34 moves matrix packages 38 in crosscurrent heat exchange fashion through the turbine discharge air from exhaust duct 26 to absorb heat from the turbine exhaust gases and through the air stream flowing through duct 18 to splitter 22 to heat the compressor discharge air.

Referring now to FIGS. 2a and 2b, it can be seen that regenerator turbine gas inlet passage 28 is an arcuately shaped opening, and regenerator turbine gas discharge outlet 30 is similarly shaped. Also, regenerator compressor air discharge outlet 2] is also arcuately shaped in a smaller arc than passage 28, and regenerator compressor air inlet passage 19 is shaped similarly to outlet 21. Rotor 34 rotates in the direction indicated by the arrows in FIGS. 2a and 2b. Thus, it can be seen that as the heat absorbing matrix packages are passed in a counterclockwise manner across the air stream from duct 18 the matrix packages transfer heat to the crossflowing compressor discharge air stream in such a manner as to produce an unevenly heated air stream at the entrance to splitter 22.

The production of this unevenly heated air stream can best be understood by reference to FlG. 3. As rotor 34 moves counterclockwise to pass matrix packages 38 from right to left across the entrance to splitter 22, the matrix packages, which constitute a heat source, are progressively cooled through interaction with the crossflowing compressor discharge stream so that the matrix packages have less heat available to transfer to the air stream as the matrix packages move counterclockwise. Thus, in a typical installation there might be a tem perature differential of as much as 200 between the temperature of the air entering splitter 22 at right wall 40 and the temperature of the air entering splitter 22 at left wall 42. For example, the temperature ofthe air stream entering splitter 22 in the vicinity of wall 40 might be l2()()F. while the temperature of the air entering splitter 22 in the vicinity of wall 42 might be l()()().lt is desirable to eliminate or reduce this air temperature differential before delivery of the air to the combustion chamber in order to avoid problems such as uneven combustion resulting from the unevenly heated air.

Referring again to FIGS. 2a and 3, twisted splitter 22 ofthe present invention operates to eliminate or reduce the temperature differential in the air stream and produce a relatively even temperatured air stream for delivery to the combustion chamber. Splitter 22 has side walls 40 and 42 extending between and joining arcuate top and bottom walls 44 and 46, respectively; the walls 40, 42, 44, and 46 cooperating to define a duct 48. The inlet to duct 48 is in flow communication with outlet 21 of the regenerator structure whereby duct 48 receives an entering air flow stream having a temperature gradient across the stream, and the outlet from duct 48 is in flow communication with the combustion chamber of the engine. The temperature gradient across the entrance to duct 48 is from a higher level at wall 40 to a lower level at wall 42.

The splitter device for accomplishing the desired mixing is a sheet metal divider element 50 which extends along the length of duct 48 from the entrance to the exit of the duct. The front edge 52 ofdivider 50 is curved from the junction of walls 40 and 46 in the lower right-hand corner 54 of the duct entrance to the junction of walls 42 and 44 in the upper left corner 56 of the entrance to the duct. The left side edge 58 of divider 50 then extends through duct 48 from corner 56 downwardly along side wall 42 to lower left corner 60 at the junction of walls 42 and 46 at the exit of splitter 22; and the right edge 62 of divider 50 extends through duct 48 upwardly along wall 40 to the upper right corner 64 at the junction of walls 44 and 40. The rear edge 66 of divider 50 is curved from corner 60 upwardly to corner 64 so that the front and rear edges 52 and 66, respectively, are curved across the inlet and outlet of duct 48 and are crossed with respect to each other, and divider 50 is twisted along the length of duct 48 in its transition from front curved edge 52 to the crossed rear edge 66 to divide duct 48 into two sections, i.e. an upper part and a lower part.

As the unevenly heated air stream from regenerator outlet 21 enters duct 48, it is divided into two parts, one part flowing between divider 50 and upper wall 44 in the upper section of the duct, and the other part flowing between divider 50 and lower wall 46 in the lower section of the duct. Referring to that portion of the stream between divider 50 and upper wall 44, the relatively hot air on the right side sees a large crosssectional flow area as it enters duct 48, and the cross-sectional flow area seen by the rest of that portion of the stream at the duct entrance diminished toward the left side of the entrance. However, as this upper part of the flow stream passes along duct 48 toward the duct exit, the cross-sectional flow area on the right side diminishes along the length of the duct and the cross-sectional flow area toward the left side increases along the length of the duct to the extent that the cross-sectional flow area at the exit is substantially the reverse of the crosssectional flow area at the entrance. This diminishing of the flow area along the right part of duct 48 and the increasing of flow area along the left part of duct 48 causes the hotter air on the right side to move toward the left of the duct and mix with the less warm air on the left side of the duct along the entire length of the duct so that this upper part of the air stream is relatively thoroughly mixed to a relatively uniform temperature at the exit from splitter 22.

Similarly, the cross-sectional area seen by the lower part of the air stream in the lower section of duct 48 between divider 50 and lower wall 46 at the entrance to duct 48 goes from a minimum on the right side to a maximum on the left side and varies along the length ofduct 48, in a reverse manner to that of the upper section, to a maximum on the right side and a minimum on the left side. This varying of cross-sectional flow area experienced by the lower part of the stream along the length ofduct 48 also causes this lower part of the stream to mix along the length of duct 48 to produce a relatively thoroughly mixed and relatively uniform temperature stream at the exit.

Both the upper and lower parts of the air stream are, of course, at the same uniform temperature level at the exit from splitter 22 so that these two parts of the stream recombine to produce a single uniform temperature stream for delivery to the combustion chamber. This equalization of temperature is brought about by interaction between the changing cross-sectional flow area at the entrance to duct 48 and the reversed varying flow areas along the lengths of the upper and lower sections of the duct, plus the fact that the heat source, comprised of matrix packages 38, is moving across the entrance to duct 48 and is changing in temperature as it passes across the entrance to duct 48. The entering cross-sectional flow area of the upper part of duct 48 decreases from right to left (as seen in FIGS. 2:: and 3), and the entering cross-sectional flow area of the lower part increases from left to right. However, progressing along the length of duct 48 toward the exit, the cross-sectional area immediately starts to change do wnstream of the entrance whereby the larger cross-sectional flow areas are diminished and the smaller areas are increased along the length of the duct 48 from the entrance to the exit. The changing flow areas along the length of the duct has two effects. One effect is that it causes the air entering at the larger side of each part of the duct to be moved or "squeezed" over to the opposite side ofthat of the duct which is enlarging proportionally to receive the air thus moved over. The other effect is that it influences the amount of air flow entering the larger entering portions of the duct to the extent that it reduces the entering airflow below that which it would otherwise be because of the reduction in flow area linearly downstream of the entrance. These dual effects and the fact that the heat source which is moving across the entrance to duct 48 and being reduced in temperature as it so moves combine to produce an equal and uniform temperature level at the exit from both the upper and lower parts of the duct 48.

It will be noted that proper functioning ofthe present invention requires the previously described changes in cross-sectional flow area along the length of the upper and lower parts of duct 48. The shape of splitter 22 as shown herein wherein the walls 44 and 46 are arcuate is particularly suited for the purposes ofthis invention. Walls 44 and 46 are preferably arcs While a preferred embodiment has been shown and described, various modifications and substitutions may be made without departing from the spirit and scope of this invention. Accordingly, it is tobe understood that this invention has been described by way of illustration rather than limitation.

lelaim:

1. Apparatus for mixing a fluid stream having a temperature differential therein to reduce said temperature differential, said apparatus including:

a duct having top and bottom surfaces and first and second spaced apart side walls extending between said top and bottom surfaces,- said top and bottom surfaces being in the shape of arcs of concentric circles, said top and bottom surfaces and said side walls cooperating to define an inlet and an outlet for said duct;

movable heat source means movable across said inlet to said duct,'said heat source means having a temperature differential thereacross; and

sheet element splitter means in said duct for mixing fluid flowing through said duet, one end of said sheet element extending in a curve substantially from the intersection of said bottom surface and one of said side walls to the intersection of said top surface and the other of said side walls, and the other end of said sheet element extending in a curve substantially from the intersection of said bottom surface and said other of said side walls to the intersection of said top surface and said one side wall, said sheet element splitter means cooperating with said top and bottom surfaces of said duct to define two duct sections of variable cross-sectional area along the length of said duct sections.

2. Apparatus for mixing a fluid stream as in claim I wherein said sheetelement is twisted along said duct uniformly from said one end ofsaid sheet element to said other end of said sheet element, the cross-sectional areas of said duct sections varying in a reversemanner along the length of said duct.

3. Apparatus for mixing a fluid stream as in claim 2 wherein an edge of said sheet element extends along said duct from said one end of said sheet element at said one side wall upwardl'y to said other end of said sheet element at said one side, and wherein another edge of said sheet element extends along said duct from said one end of said sheet element at said other side wall downwardly to said other end of said sheet element at said other side wall.

4. Apparatus for mixing a fluid stream as in claim 1 wherein said side walls are disposed between said top and bottom surfaces along radial lines of said circles 5. Apparatus for mixing a fluid stream as in claim I wherein said heat source means has a decreasing temperature in the direction of movement across said inlet. 

